The two major types of solar charge controllers are:
As shown in the chart below, PWM controllers tend to be smaller and they operate at battery voltage, whereas MPPT controllers use newer technology to operate at the maximum power voltage. This maximizes the amount of power being produced which becomes more significant in colder conditions when the array voltage gets increasingly higher than the battery voltage. MPPT controllers can also operate with much higher voltages and lower array currents which can mean fewer strings in parallel and smaller wire sizes since there is less voltage drop.
PWM controllers need to be used with arrays that are matched with the battery voltage which limits what modules can be used. There are many 60 cell modules with maximum power voltage (Vmp) equal to about 30V, which can be used with MPPT controllers but are simply not suitable with PWM controllers.
To answer the question: Which is better, PWM or MPPT? All things being equal, MPPT is a newer technology that harvests more energy. However, the advantages of MPPT over PWM controllers come at a cost, so sometimes a less expensive PWM controller can be the right choice, especially with smaller systems and in warm climates where the MPPT boost is not as significant.
PWM vs. MPPT Solar Charge Controller Comparison
|PWM Controllers||MPPT Controllers|
|Array voltage is “pulled down” to battery voltage||Convert excess input voltage into amperage|
|Generally operate below Vmp||Operate at Vmp|
|Suitable for small module configurations||Suitable for large module configurations that have a lower cost per watt|
|Often chosen for very hot climates which will not yield as much MPPT boost||Provide more boost than PWM, especially during cold days and/or when the battery voltage is low|
Every Morningstar PWM and MPPT solar charge controller is listed on the Morningstar Product Series page. Each listed product is hypertext linked to its product page that includes datasheets, operation manuals, and other helpful information.